Physiological responses during exposure to carbon dioxide and bioeffluents at levels typically occurring indoors

Abstract

Twenty-five subjects were exposed to different levels of carbon dioxide (CO ) and bioeffluents. The ventilation rate was set high enough to create a reference condition of 500 ppm CO with subjects present; additional CO was then added to supply air to reach levels of 1000 or 3000 ppm, or the ventilation rate was reduced to allow metabolically generated CO to reach the same two levels (bioeffluents increased as well). Heart rate, blood pressure, end-tidal CO (ETCO ), oxygen saturation of blood (SPO ), respiration rate, nasal peak flow, and forced expiration were monitored, and the levels of salivary α-amylase and cortisol were analyzed. The subjects performed a number of mental tasks during exposures and assessed their levels of comfort and the intensity of their acute health symptoms. During exposure to CO at 3000 ppm, when CO was added or ventilation was restricted, ETCO increased more and heart rate decreased less than the changes that occurred in the reference condition. Exposure to bioeffluents, when metabolically generated CO was at 3000 ppm, significantly increased diastolic blood pressure and salivary α-amylase level compared with pre-exposure levels, and reduced the performance of a cue-utilization test: These effects may suggest higher arousal/stress. A model is proposed describing how mental performance is affected by exposure to bioeffluents.

Human responses to carbon dioxide, a follow-up study at recommended exposure limits in non-industrial environments

“…4). This is consistent with the results obtained in the previous study by Zhang et al (2016a), where the similar trend was observed during exposure to pure CO 2 at 3,000 ppm (the levels of ETCO 2 was then 5.4 kPa).…”

“…In the previous study by Zhang et al (2016a), heart rate data were available for 25 subjects and the exposure time was 4.5 hours.…”

“…Schaefer, 1979;Law et al, 2010;Zhang et al, 2016a), it seems possible that poor performance of the SMS test could be due to other reasons. It may be postulated that reduced performance occurred because of the elevated stress/arousal level of individuals taking the test.…”

“…the current 8-hour occupational exposure limit set by the Occupational Safety and Health Administration (OSHA) (CCOHS, 2005) and the American Conference of Governmental Industrial Hygienists (ACGIH, 2011); the ceiling limit of 30,000 ppm for 10-minute exposure set by ACGIH is only relevant for industrial exposures as it is highly unlikely that it would occur in non-industrial settings. As summarized in the literature survey performed by Zhang et al (2016a), at levels below 10,000 ppm no toxic effects of CO 2 are expected, and even no physiological responses due to CO 2 exposures were observed that could plausibly lead to negative health effects. The published studies show that M A N U S C R I P T…”

Real-time monitoring of personal exposures to carbon dioxide

“…Zhang et al [17,18] reported measures of cognitive impacts and physiological responses to elevated CO2 exposures lasting 255 min resulting from either injection of pure CO2 or via reduced ventilation in relation to human metabolic emissions. During experiments in which CO2 was injected, Zhang et al [17] report no statistically significant effects on perceptions of air quality, acute health symptoms, or cognitive impacts.…”